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UC-NRLF 


Uw-~— 

tec         CONSTRUCTION  AND   MANUFACTURE  OF 

£     AUTOMOBILES 


BY  RALPTI  E   Fr  ANDERS 
SECCivD 


MACHINERY'S   REFERENCE  «QT.vRlEb- 

PUBLISHED  bY  MAC    TINLRY,  NEW  YORK 


MACHINERY'S  REFERENCE  SERIES 

EACH   NUMBER    IS    A    UNIT    IN    A    SERIES   ON    ELECTRICAL    AND 

STEAM    ENGINEERING    DRAWING    AND    MACHINE 

DESIGN    AND    SHOP    PRACTICE 


NUMBER  60 

CONSTRUCTION 

AND  MANUFACTURE  OF 

AUTOMOBILES 

By  RALPH  E.  FLANDERS 
SECOND  EDITION 

CONTENTS 

Design  and  Construction  of  a  High-grade  Motor  Car       -      3 
Automobile  Manufacturing  Methods    -  18 

Manufacturing  Equalizing  Gears 31 


Copyright,  1912,  The  Industrial  Press,  Publishers  of  MACHINERY. 
49-55  Lafayette  Street,  New  York  City 


CHAPTER  I 


DESIGN  AND   CONSTRUCTION   OP  A 
HIGH-GRADE  MOTOR  CAR* 

The  following  description  of  a  40  H.  P.  automobile,  built  by  tuc 
Stevens-Duryea  Company,  of  Chicopee  Falls,  Mass.,  may,  except  for 
certain  important  details  which  will  be  specifically  mentioned,  be 
taken  as  typical  of  the  design  of  high-grade  cars  in  general.  In  Fig. 
1  is  shown  a  side  view  of  the  "Model  Y,"  40  horsepower,  six-cylinder 
machine,  with  36-inch  wheels  and  142-inch  wheel-base.  An  automobile 
may  be  divided  into  two  parts— the  body  and  the  "chassis."  The  former 
is  the  product  of  the  carriage-maker's  art,  the  latter  of  the  mechanic's 


Fig.  I.    Stevena-Duryea  "Big  Six"  Motor  Car,  191O  Model 

and  engineer's.     The  chassis  of  this  machine  is  shown  in  Figs.  2  and 
3,  to  which  reference  will  now  be  made. 

The  mechanism  and  body  of  the  car  are  supported  by  a  frame  whose 
side  members,  of  chrome-nickel  steel,  are  shown  at  A.  These  are 
connected  by  four  cross  pieces,  and  are  supported  on  the  front  and 
rear  axles  by  the  spring  connections  shown.  The  cross  pieces  are 
also  pressed  from  chrome-nickel  steel,  and  are  hydraulically  riveted 
to  the  side  frames.  A  platform  spring  suspension  is  used  at  the  rear, 
hung  on  connecting  shackles  designed  to  overcome  the  side  roll  met 


*  MACHINERY,  October,  1909. 


347614 


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DESIGN  OF  A  HIGH-GRADE  MOTOR  CAR 


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No.  60— AUTOMOBILE  CONSTRUCTION 


available  horsepower  per  hundredweight  of  load.  It  also  permits  the 
power  plant  to  be  assembled  as  a  whole  and  to  be  bolted  in  place  with- 
out fitting.  This  construction,  which  is  the  distinctive  point  in  the 
design  of  this  motor,  has  been  successfully  followed  by  the  builders 
for  the  last  five  years,  and  it  is  one  of  the  things  which  serve  to  give 
an  attractive  mechanical  appearance  to  the  whole  mechanism.  Only 
one  double  set  of  universal  joints  is  required,  that  connecting  the 
propeller  shaft  with  the  transmission  gearing  at  one  end,  and  the 
differential  gearing  at  the  other. 

The  cylinders  are  grouped  in  three  two-cylinder  castings  C,  bolted 
to  the  crank  case  N.  As  is  common  with  internal  combustion  engines 
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DESIGN  OF  A  HIGH-GRADE  MOTOR  CAR 


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8 


No,  60— AUTOMOBILE  CONSTRUCTION 


at  the  forward  end  of  the  erank-shatt,  as  here  shown,  is  unusual,  the 
common  construction  being  to  locate  it  between  the  crank-shaft  and 
the  clutch.  It  tends,  in  particular,  to  bring  more  of  the  weight  onto 
the  front  wheels,  off  from  the  heavily  loaded  rear  wheels  of  the  ma- 
chine, and  permits  the  reducing  of  the  clearance  over  the  roadbed  in 
ib*  center  of  the  chassis,  where  there  is  the  greatest  danger  of  strik- 
ing on  high  water-bars,  railroad  crossings,  etc.  It  will  be  readily 
«een  that  more  clearance  is  required  at  the  center  of  the  machine 
than  at  the  axles,  when  crossing  a  hump  in  the  road. 

Lubrication,  Ignition,  etc. 

Two  shafts  mounted  in  the  crank  casing,  one  on  each  side,  above  and 
parallel  to  the   crank-shaft,  are  driven  from   it  by  enclosed   gearing. 


Fig.  6.    View  of  Engine  from  Beneath,  showing  Removal  of  Piston,  Cam- 
and  Lay-shafts,  etc.,  without  Dismantling 

The  one  at  the  side  shown  in  Fig.  5  is  the  cam-shaft  and  is  provided 
with  twelve  sets  of  cams  for  operating  the  six  inlet  and  six  exhaust 
valves,  whose  stems  and  closing  springs  are  plainly  shown  in  the 
engraving.  The  driving  gear  of  this  cam-shaft  is  also  connected  with 
a  pinion  on  the  armature  shaft  of  the  magneto,  whose  function  will 
be  described  later.  The  shaft  on  that  side  of  the  machine  shown  in 
Fig.  4,  is  known  as  the  lay-shaft.  Its  office  is  the  driving  of  the  timer 
Y,  which  controls  the  ignition,  the  driving  of  the  forced  lubrication 
mechanism  at  W,  and  of  the  water  jacket  circulation  pump  0. 

The  lubricator  gives  a  forced  oil  supply  with  sight  feed,  and  is 
always  in  operation  when  the  engine  is  in  motion.  The  six-throw 
crank-shaft  is  mounted  in  four  bearings  in  the  crank  case,  with  two 
cranks  between  each  pair  of  bearings.  The  boxes  at  these  points  are 
connected  with  the  lubricator  W.  The  lower  half  of  the  crank  case 
forms  a  reservoir  for  the  oil  escaping  from  the  main  bearings.  The 
connecting-rod  splashes  into  this  and  thus  supplies  the  pistons,  con- 
necting-rod bearings,  etc.,  with  the  necessary  lubrication. 


DESIGN  OF  A  HIGH-GRADE  MOTOR  CAR 

The  ignition  in  each  cylinder  is  effected  by  either  of  two  systems, 
the  one  by  storage  or  dry  battery  and  induction  coil,  and  the  other 
by  means  of  a  magneto  U  connected  by  gearing  with  the  crank-shaft. 
The  battery  and  spark  coil  is  used  in  starting,  while  the  magneto  is 
used  for  regular  running.  The  spark  coils  and  switches  are  located 
on  the  dashboard.  A  lever  on  the  steering  wheel,  as  will  be  described, 
is  connected  with  the  commutator  or  timer  T7.  which  distributes  the 
current  to  the  six  cylinders  in  such  a  way  as  to  enable  the  operator 
to  advance  or  retard  the  spark  at  will. 

The  Carburetor  and  Fuel  Supply 

An  important  and  rather  delicate  piece  of  apparatus  essential  to  the 
operation  of  the  gasoline  engine,  is  the  carburetor,  shown  at  Z  in 


Fig.  7.     Clutch  and  Transmission  Gear  Members  Dismantled 
to  show  Construction 

Fig.  5.  This  receives  a  supply  of  gasoline  through  a  feed  pipe  from 
the  tank  G  (see  Fig.  2),  a  supply  of  air  through  T  heated  by  the 
exhaust  gas  for  vaporizing  the  gasoline,  and  a  supply  of  fresh  air 
to  furnish  the  oxygen  for  the  charge.  The  gasoline  is  received  in  a 
float  chamber,  where  the  level  of  the  liquid  is  maintained  by  a  suitable 
float  and  valve.  An  automatic  valve  provides  for  a  constant  propor- 
tion of  oxygen  and  fuel  at  widely-varying  speeds.  The  carburetor  is 
provided  with  a  throttle  which  controls  the  needle  valve  connection 
in  the  feed  pipe,  together  with  the  butterfly  valve  in  the  suction  to 
the  cylinders,  thus  providing  the  driver  with  means  for  varying  the 
amount  of  charge  furnished  the  machine;  this  controls  the  speed 
without  shifting  the  gears  in  the  transmission  case.  The  automatic 
air  valve  is  controlled  from  the  seat  by  a  handle  Y  on  the  dash-board, 
which  permits  the  obtaining  of  a  proper  mixture  for  the  starting.  A 
button  at  the  front  of  the  radiator,  where  the  machire  is  cranked  for 


10 


No.  60— AUTOMOBILE  CONSTRUCTION 


starting,  also  provides  means  for  flooding  the  carburetor  with  fuel 
for  a  send-off.  The  throttle  is  controlled  from  a  lever  on  the  steering 
wheel,  concentric  with  the  spark  control  lever,  or  from  an  "accelerator 
pedal"  on  the  foot-board. 

The  gasoline  supply  tank  O  is  located  under  the  front  seat.  It  con- 
tains a  partition  near  the  bottom  which  saves  about  three  gallons  out 
of  its  twenty  gallons'  capacity,  for  use  in  emergency.  By  the  manipu- 
lation of  cut-off  valves  passing  through  the  left  side  frame  of  the 
chassis,  it  is  possible  to  use  this  reserve  supply  after  the  tank  has 
.been  otherwise  exhausted.  This  provision  is  a  great  comfort  to  the 
motorist  at  critical  times. 

The  Clutch  and  the  Transmission  Gearing 

In  casing  E  is  mounted  the  clutch  Z  (Fig.  7)  connecting  the  engine 
with  the  transmission  to  the  driving  wheels.  This  is  of  the  multiple 


Slack  inery,N.Y 


Fig.  8.    Sketch  showing  Arrangement  of  Gears  in 
Transmission  Case 

disk  type,  with  alternate  disks  keyed  to  the  driving  and  driven  mem- 
bers. The  driving  disks  have  a  wired  asbestos  facing  which  makes 
a  superior  friction  surface,  and  gives  a  high  resistance  to  heat  as 
well.  This  construction  obviates,  and  in  fact  makes  impossible,  the 
use  of  oil  in  the  clutch.  The  friction  surfaces  are  held  in  engage- 
ment by  a  spring,  and  are  released  by  a  pedal  Blt  which  projects 
through  the  foot  board  at  the  driver's  side  of  the  machine.  The 
spring  is  so  proportioned  as  to  give  a  smooth,  easy  engagement,  en- 
tirely out  of  the  control  of  the  driver,  who  thus  finds  it  impossible 
to  start  the  machine  with  a  sudden  shock.  The  second  foot  lever,  Clt 
is  connected  with  the  rear  wheel  brakes,  as  will  be  described.  The 
driven  member  of  the  clutch  is  connected  with  the  driving  shaft  in 
the  transmission  case  or  speed  box  F.  Contained  within  it  is  a  mechan- 
ism which,  by  the  aid  of  the  sliding  gears,  clutches,  etc.,  permits  of 
the  obtaining  of  three  forward  and  one  reverse  speed. 

The  operation  of  this  gearing  will  be  understood  from  the  sketch 
shown  in  Fig.  8.  Gear  A,  receives  its  movement  from  the  clutch.  It 
meshes  with  gear  Dt  keyed  to  the  secondary  shaft  E,,  which  is  thus 
in  motion  whenever  the  engine  is  running  and  the  clutch  is  engaged. 
This  shaft  carries  also  gears  Gn  #„  and  Wlt  the  latter  of  which  drives, 
in  turn,  the  idler  X^  Squared  shaft  Yj  is  directly  connected  by  means 


DESIGN  OF  A  HIGH-GRADE  MOTOR  CAR 


11 


of  propeller  shaft  J  (Fig.  3)  and  the  universal  joints  with  the  rear 
axle.  On  Ya  is  mounted  the  double  sliding  gear  Zt.  Clutch  teeth  are 
provided  in  the  faces  of  the  gears  A,  and  Jlt 

In  the  position  shown  in  Fig.  8,  the  transmission  is  in  the  neutral 
position,  so  that  the  motion  from  the  clutch  is  not  transmitted  to  the 
axle.  The  right-hand  end  of  shaft  Yj  lies  loosely  in  the  revolving  gear 
AI.  When  the  sliding  gear  is  thrown  to  the  extreme  right,  the  clutch 
faces  of  Aj  and  Jt  are  engaged,  so  that  shaft  Y,  is  driven  directly, 
and  at  the  highest  speed,  from  the  clutch.  By  shifting  it  a  step  to 


Fig.  9.    The  Speed  Gear  Control  and 
Emergency  Brake  Levers 

the  left,  /!  is  thrown  into  mesh  with  Glf  thus  giving  a  lower  rate  of 
speed  through  the  back  gear  shaft  Ev.  A  still  further  movement  to 
the  left,  past  the  neutral  point  shown  in  the  engraving,  brings  Zj 
into  engagement  with  Hlt  giving  the  lowest  forward  speed.  A  final 
movement  to  the  left  engages  Z:  with  idler  Xlt  thus  reversing  the 
drive. 

The  shifting  of  gears  Z1  and  J1  is  effected  by  a  forked  lever  con- 
nected with  lever  A2  (Fig.  9)  at  the  side  of  the  machine,  which  thus 
controls  the  speed  changes.  This  lever  is  provided  with  a  latch  con- 
nected with  a  pin  in  the  slot  of  the  quadrant  B2,  operating  in  a  man- 
ner easily  understood  from  the  engraving.  It  will  be  seen  that  it  is 
possible  to  move  between  the  reverse  and  the  lowest  speed,  or  between 
the  second  and  the  high  speed,  without  touching  the  latch,  and  it  is 
possible  to  make  all  the  movements  rapidly  and  precisely  by  the 
sense  of  touch  without  looking  at  the  quadrant  at  all. 


12 


No.  60— AUTOMOBILE  CONSTRUCTION 
The  Differential  Drive 


Propeller  shaft  J  leads  from  the  transmission  case  F  to  differential 
case  A'  on  the  rear  axle.  The  bevel  gear  MI  (Fig.  11)  is  connected 
with  the  two  rear  wheels  by  a  differential  mechanism,  whose  function 
it  is  to  give  an  equal  tractive  force  to  each  of  the  two  wheels,  but  at 
the  same  time  to  permit  either  of  them  to  run  ahead  or  lag  behind 
the  other  as  may  be  required  in  rounding  curves,  riding  over  obstruc- 
tions, ejc.  The  principle  of  this  mechanical  movement  will  be  under- 
stood by  referring  to  Fig.  10. 

Referring  first  to  the  sketch  at  the  left,  NI  is  the  pinion  on  the  pro- 
peller shaft  and  MI  is  the  driven  bevel  gear,  concentric  with  the  axle. 


Fig.  1O.     Sketch  showing:  Principle  of  the  Bevel  and  Spur  Gear 
Types  of  Differential  Gearing: 

This  gear  and  shell  O2  to  which  it  is  bolted,  revolve  freely  on  the  hubs 
of  E2  and  F2.  Within  the  shell  are  mounted  radial  pivots  on  which 
revolve,  loosely,  bevel  pinions  D>.  These  engage  with  bevel  gears  Ey 
and  Fs,  connected  respectively  with  the  right-  and  left-hand  axle 
shafts  Tj.  It  will  be  seen  that  under  ordinary  conditions  the  rotating 
of  gear  Mt  carries  gears  E~  and  F,  along  with  it,  by  the  pull  exerted 
on  them  by  the  bevel  pinions  D..,  which  are  stationary;  thus  the  two 
rear  wheels  are  driven  at  the  same  rate  of  speed.  Suppose  now  that 
the  right-hand  wheel  be  held  from  turning,  so  that  gear  JE7,  is  station- 
ary, then  the  rotation  of  bevel  gear  M^  will  roll  pinion  D,  about  on  #2 
with  a  compound  action,  which  will  give  F,  twice  the  rate  of  speed 
it  had  before.  In  the  same  way,  F,  can  be  held  from  revolving,  in 
which  case  E2  will  have  twice  its  normal  speed,  or  either  of  them 
may  be  slowed  down,  in  which  case  the  other  is  speeded  up  corre- 
spondingly. The  driving  force  on  both  wheels,  however,  is  always 
the  same. 


DESIGN  OF  A  HIGH-GRADE  MOTOR  CAR 


13 


An  alternative  form  of  this  device  is  shown  at  the  right  of  Fig.  10, 
in  which  each  of  the  bevel  gears  D,  is  replaced  by  a  pair  of  spur  pin- 
ions D2  and  Z>'2)  meshing  with  each  other  and  with  spur  gears  E2 
and  P.,  as  shown.  A  little  study  will  show  that  the  action  of  this 
device  is  identical  with  that  shown  in  the  sketch  at  the  left  of  the 
figure,  the  only  change  being  the  employment  of  spur  gearing  in  place 
of  bevel  gearing.  The  differential  used  on  the  Stevens-Duryea  ma- 
chine is  of  the  second  or  spur  gear  type. 

The  Pull  Floating-  Type  Rear  Axle 

The  differential  gearing  is  contained  in  the  casing  0,,  which  forma 
the  central  member  of  the  axle.  Tubular  extensions  to  both  sides 


Fig.  11.    The  Full  Floating  Type  Rear  Axle,  Differential  Gearing,  etc. 

carry  the  spring  supports  P.  on  which  the  weight  of  the  car  rests. 
The  brake  flanges  Qt  and  the  wheel  bearings  at  Klf  all  of  which  are 
solid  with  each  other,  are  non-rotating.  The  rear  axle,  however,  is 
permitted  to  rock  in  spring  supports  Pt.  The  torque  rod  or  tube  £„ 
which  is  fast  in  case  Olf  extends  toward  the  center  of  the  chassis, 
where  it  is  hung  in  a  spring  suspension  as  seen  in  Fig.  3  permitting 
a  limited  vibration  up  or  down,  with  a  constant  force  urging  it  toward 
a  central  position.  This  construction  furnishes  the  resistance  against 
the  climbing  of  pinion  Nt  on  bevel  gear  Mt.  In  case  of  sudden  start- 
ing or  stopping,  a  limited  amount  of  climbing  either  way  is  permit- 
ted, the  torque  rod  being  raised  or  lowered  against  the  spring  pres- 
sure to  correspond.  This  greatly  decreases  the  danger  of  gear  breakage. 


14  Xo.  60— AUTOMOBILE  CONSTRUCTION 

The  construction  just  described  belongs  to  what  is  known  as  the 
full  floating  type  axle.  The  wheels  are  mounted  on  ball  bearings  on 
stationary  journals  J?,.  Shafts  7\  are  provided  with  squared  driving 
ends  engaging  sockets  in  the  differential  gearing  in  casing  Ot  at  one 
end,  and  similar  sockets  cut  in  driving  dogs  Ul  at  the  other  end. 
These  latter  members  hav*  driving  slots  engaging  dove-tails  in  the 
hubs  of  the  wheels,  to  which  the  power  is  thus  transmitted.  The 
squared  ends  of  shafts  7\  are  rounded  to  permit  a  slight  rocking 
movement  in  their  sockets  in  the  differential  gearing  and  driving  dogs 
U^  This  permits  the  springing  of  the  rear  axle  under  the  load  with- 
out, cramping  the  driving  mechanism. 

To  allow  for  the  springing  of  this  axle  under  the  load,  the  two 
sections  of  tubing  on  either  side,  between  members  Ox  and  Qt  ar.e 
•held  in  bored  seats  which  point  downward  at  an  angle  of  %  degree 
from  the  horizontal  on  each  side.  Thus  the  rear  axle  wheels  point  in 
toward  each  other  at  the  bottom  at  an  angle  of  */£  degree  from  the 
vertical,  giving  a  much  better  appearance  than  would  be  the  case  if 
they  should  by  some  mischance  point  the  other  way.  It  would  take  a 
load  in  excess  of  any  which  would  ever  be  applied  to  spring  the  axle 
and  bring  the  wheels  into  the  vertical  plane.  It  is  stated  that  when 
the  wheels  are  exactly  vertical,  they  have  the  appearance  of  being 
sprung  out  at  the  bottom,  into  the  position  occasionally  seen  in  a 
vehicle  of  the  "one-horse-shay"  type. 

The  Brakes 

The  brake  mechanism  of  the  automobile  is  of  the  utmost  import- 
ance, as  is  realized  by  anyone  who  has  had  anything  to  do  with  these 
machines  whether  as  driver,  passenger  or  pedestrian.  It  is  usual  to 
provide  two  complete  sets  of  braking  machanism,  one  for  regular  use 
and  the  other  for  emergency.  That  for  regular  use  is  controlled  by 
the  foot  lever  Cl  (see  Fig.  4),  which  is  connected  with  a  reach  rod 
leading  to  double  cranks  on  a  transverse  rock-shaft  at  Vt  (Fig.  3). 
One  section  of  this  rock-shaft  is  connected  with  the  brake  at  the  right 
side  of  the  machine,  and  the  other  at  the  left.  An  equalizing  lever 
between  the  two  insures  an  even  pressure  on  each  of  these  two  brakes, 
even  though  one  be  much  more  worn  than  the  other.  The  brake  is 
of  the  band  type,  applied  to  the  outside  of  a  brake  rim  fast  to  the  hub 
of  the  wheel.  The  emergency  brake  is  operated  by  lever  C2  (Fig.  2). 
This,  by  means  of  a  second  rock-shaft  concentric  with  Vlt  controls 
internal  expanding  ring  brakes  in  the  hubs  of  the  wheels. 

The  Control  of  the  Machine 

The  steering  gear  will  be  best  understood  from  Figs.  2,  3  and  12. 
The  wheel  Ft  is  mounted  on  a  tubular  shaft  which  carries  at  its  lower 
end  a  worm  engaging  the  segment  of  a  worm-wheel  G2  in  casing  Elt 
To  the  hub  of  this  segment  is  connected  a  bell  crank  //.,  which, 
through -the  operation  of  the  steering  rod  L^  (see  Fig.  2)  and  suitable 
connecting  cranks  and  links,  turns  the  front  wheels  to  the  right  or 
left  as  may  be  required.  Spring  cushions  are  provided  at  the  ends  of 
steering  rod  Li  so  that  sudden  shocks  and  twists  of  the  wheels  are 


DESIGN  OF  A  HIGH-GRADE  MOTOR  CAR 


15 


not  transmitted  to  the  worm-gearing  and  the  steering  wheel,  even 
when  traveling  at  a  high  rate  of  speed.  As  most  mechanics  doubt- 
less know,  the  center  line  of  the  pivots  about  which  the  wheels  are 
swiveled  meets  the  road  at  about  the  point  where  the  tire  touches  it. 
This  makes  it  possible  to  turn  the  wheels  easily  when  standing  still, 
and  decreases  the  danger  of  accident  while  running,  as  well. 

As   previously   stated,   the   throttle   control   and   the   timing   of   the 
spark  are  effected  frcm  levers  placed  at  the  hub  of  the  steering  wheel. 


Fig.  12.    The  Steering  Post,  with  its  Throttle  and  Sparking  Connections 

Lever  K2  controls  the  throttle.  This  is  mounted  on  a  tube  passing 
through  the  steering  wheel  tube  and  connected  at  its  lower  end  by 
bevel  gear  segments  with  a  bell  crank  L2,  which  is,  in  turn,  con- 
nected by  suitable  rods  and  levers  with  the  carburetor.  Inside  of  the 
throttle  lever  tube  is  still  another  fixed  tube  on  which  is  mounted 
the  segment  Af2,  which  is  thus  held  stationary.  This  is  provided  with 
notches  for  locating  lever  K»,  and  lever  /2  as  well,  which  latter  con- 
trols the  timing  of  the  spark.  This  is  mounted  on  a  rod  which  passes 
through  the  center  of  the  system  of  tubes  and  is  connected  by  bevel 
segments  with  lever  N*  leading  to  the  commutator  or  tinier  V. 


16  No.  60— AUTOMOBILE  CONSTRUCTION 

It  may  be  well  to  recapitulate  as  to  the  functions  of  the  levers,  etc., 
used  in  the  control  of  the  machine.  At  the  front  of  the  radiator  is 
the  crank  by  which  the  motor  is  turned,  for  starting.  By  the  side 
of  it  is  a  button  connected  with  the  carburetor,  for  flooding  the  latter 
at  starting  to  obtain  a  rich  mixture  on  the  first  stroke.  On  the  dash- 
board is  mounted  a  lever  3',  for  setting  the  automatic  air  valve  to 
supply  the  proper  amount  of  oxygen  for  starting.  Beside  it  is  a 
switch  for  throwing  the  ignition  spark  from  the  battery  to  the  mag- 
neto when  the  machine  is  changed  from  the  starting  to  the  running 
condition,  and  vice  versa.  On  the  dashboard  are  also  mounted  the 
spark  coils.  Through  the  foot  board  project  the  two  pedals  Bl  andCt 
controlling  the  clutch  and  the  operating  brake  respectively,  as  de- 
scribed. Hand  lever  C,  and  A,  control  the  emergency  brake  and  the 
speed  changes  respectively. 

Two  small  pedals  are  also  provided  on  the  foot  board.  One  of 
these  is  connected  with  the  throttle  in  such  a  way  that  this  may  be 
controlled  by  the  foot  instead  of  by  the  hand  if  required.  It  is  called 
the  accelerator.  By  its  use,  when  the  hand  throttle  lever  has  been 
set  to  a  certain  point,  the  valve  may  be  opened  clear  out  to  the  maxi- 
mum, as  desired,  by  the  foot,  thus  giving  immediate  control  under 
varying  conditions  of  traffic.  The  other  pedal  operates  a  valve  which 
cuts  out  the  muffler.  This  is  occasionally  done  to  make  the  exhaust 
audible,  for  finding  out  how  the  engines  are  working,  and  also  for 
removing  the  back  pressure,  and  thus  giving  every  ounce  of  power 
possible  on  critical  occasions. 

These  levers,  pedals,  etc.,  with  the  main  and  supplementary  gaso 
line  supply  valves  previously  mentioned,  give  the  driver  complete 
control  of  a  powerful,  swift  machine,  if  he  has  the  knowledge,  experi- 
ence and  nerve  to  use  them  properly. 

General  Considerations  in  Automobile  Design 

A  glance  at  the  illustrations  will  serve  to  show  that  the  chassis 
of  the  modern  high-power  automobile  is  a  rather  complicated,  highly 
specialized,  and  carefully  designed  piece  of  mechanism.  It  is  within 
the  memory  of  the  child  in  kindergarten  when  this  was  not  the  case, 
and  the  writer  has  painful  memories  of  his  duties  as  consulting  phy- 
sician to  one  of  the  best  of  the  machines  in  existence  six  years  ago 
At  that  time,  the  mechanism  of  the  automobile  did  not  have  the  homo- 
geneous, appropriate  structure  that  the  successful  machines  of  the 
present  day  jmssess.  It  had  a  gasoline  engine,  an  epicyclic  speed 
change  mechanism,  a  jack-in-the-box  differential  gear,  and  chains 
leading  to  the  rear  wheels  of  a  "horseless  carriage."  Over  the  mechan- 
ism thus  described  wandered  a  maze  of  levers,  braces,  pipes,  wires, 
etc.,  supported  at  intervals  at  any  part  of  the  mechanism  which  hap- 
pened to  be  in  convenient  reach.  That,  however,  was  before  the  auto- 
mobile "found  itself."  The  present  development  has  been  the  result 
of  the  experience  of  many  men  with  break-downs  and  failures,  as  well 
as  of  an  enormous  amount  of  theoretical  work  in  the  matter  of  test- 
ing of  materials  and  analysis  of  conditions.  These  theoretical  and 
practical  results  have  been  combined  on  the  drawing  board,  and  the 


DESIGN  OF  A  HIGH-GRADE  MOTOR  CAR  17 

resulting  machine  has  the  appearance  of  having  been  designed  rather 
than  simply  built. 

The  guiding  principles  in  the  design  of  the  automobile  relate  to 
strength,  power,  lightness,  durability,  accessibility,  and  economy  in 
operation.  The  matter  of  economy  in  construction  and  materials  is 
about  the  last  thing  to  be  thought  of,  instead  of  the  first,  as  with 
many  other  classes  of  machinery.  The  severe  and  often  reckless  usage 
received  by  one  of  these  machines  demands  special  treatment  in  the 
design  and  construction  which  should  not  ordinarily  be  necessary. 

As  an  illustration  of  what  has  been  said  in  this  respect,  attention 
may  be  called  to  the  method  of  connecting  the  driving  members  of 
this  machine,  from  the  engine  through  to  the  wheels.  In  no  place 
throughout  the  length  of  the  chassis  are  keys  used  for  this  work.  Reli- 
ance is  everywhere  placed  on  square  joints  or  dovetailed  flanges.  The 
crank-shaft  is  connected  with  the  .driving  member  of  the  clutch  by  a 
square  taper  socket.  The  driving  member  of  the  clutch  is  connected 
by  a  square  socket  with  the  driving  shaft  of  the  transmission  gear- 
ing. The  sliding  gears  of  this  mechanism  are  mounted  on  square 
shafts,  and  the  same  squared  drive  is  used  for  the  universal  joints, 
propeller  shafts,  pinion  shafts,  etc.,  through  the  intermediate  pinions 
in  the  differential  gearing  at  Ml  in  Fig.  11,  and  through  driving  shafts 
Tv  to  the  driving  dogs  on  the  wheel  hubs.  These  latter,  as  well  as 
the  side  plates  of  the  differential  gearing,  drive  or  are  driven  by 
the  engagement  of  dovetailed  teeth.  The  possibility  of  the  shearing 
of  keys,  always  present  in  machine  parts  subject  to  shock,  is  thus 
avoided.  The  makers  believe  themselves  to  be  the  only  firm  employ- 
ing a  complete  drive  of  this  kind. 

In  the  matter  of  accessibility,  a  study  of  Figs.  6  and  7  will  be  found 
interesting.  By  removing  the  lower  crank  chamber  casing  and  turn- 
ing the  crank-shaft  to  the  proper  position,  the  piston  and  piston  rod 
may  be  removed  without  further  trouble,  and  without  removing  cylin- 
ders or  cylinder  heads.  The  same  is  true  of  the  cam-  and  lay-shafts. 
The  covers  provided  for  the  clutch  and  transmission  casings  give  evi- 
dence of  care  in  providing  easy  means  for  inspection  and  removal  of 
all  parts  likely  to  need  attention.  With  a  well-designed  machine  the 
man  on  his  back  under  the  motor  car  is  a  mere  figment  of  the  imagina- 
tion. 


CHAPTER  II 


AUTOMOBILE  MANUFACTURING  METHODS* 

The  subserviency  of  manufacturing  considerations  to  considerations 
of  strength,  durability,  accessibility,  etc.,  mentioned  in  the  preceding 
chapter,  results  in  the  design  of  parts  which  require  special  and  inter- 
esting provisions  for  their  economical  production.  Only  a  few  of  the 
operations  particularly  noticed  in  the  Stevens-Duryea  factory  will  be 
described  here.  They  will  serve,  however,  to  give  an  idea  of  the  gen- 
eral practice  in  such  work,  and  will  illustrate  the  ingenuity  required 
for  the  solution  of  some  of  the  problems. 

Operations  in  the  Machining-  of  Cylinders 

In  Fig.  13  is  shown  a  Beaman  &  Smith  combined  horizontal  and 
vertical  milling  machine  engaged  in  surfacing  the  base,  exhaust  and 


Fig.  13.    Gang  Milling  Operation.    Surfacing  Cylinder  Sides  and  Ends 


inlet  flanges,  and  the  spark  plug  bosses  of  a  series  of  cylinder  castings. 
The  work  is  mounted  in  gangs  according  to  the  most  approved 
methods.  The  picture  is  chiefly  interesting  in  that  it  shows  that  the 
builders  take  advantage  of  wholesale  manufacturing  methods  even  in 
the  building  of  a  $4,000  machine.  Of  course,  an  extensive  use  of  jigs 
and  fixtures,  besides  reducing  the  cost  of  manufacture,  results  in  a 
greater  uniformity  in  the  product,  and  thus  gives  the  advantage  of 
an  easy  renewal  of  worn  or  damaged  parts. 

Fig.  14  shows  a  Beaman  &  Smith  boring  machine  with  fixtures  mount- 
ed on  the  rotating  table  for  holding  four  double  cylinder  castings. 
This  table  can  be  rotated  and  adjusted  across  the  bed  of  the  machine. 


*  MACHINERY,  October,  1909. 


MANUFACTURING  METHODS 


19 


On  each  side  of  the  table,  double  boring  heads  may  be  fed  in  along 
the  bed,  one  carrying  roughing  and  the  other  finishing  cutters,  the 
feeds  and  speeds  of  the  two  heads  being  independent.  A  set  of  two 
castings  being  in  place  on  the  roughing  end,  the  head  is  fed  into 
them  and  one  hole  in  each  casting  is  roughed  out.  The  work-table  is 


Fig.  14.    Four-cylinder  Boring  Machine  with  Revolving  Table 


Fig.  15.     Grinding  the  Cylinders.    Note  Connections  for  Exhausting  the 
Dust  and  the  Use  of  the  Water  Jacket  for  Cooling 

then  shifted,  by  means  of  the  hand-wheel,  against  suitable  stops,  and 
the  other  bore  of  each  cylinder  is  roughed.  The  table  is  then  indexed 
to  bring  these  castings  to  the  finishing  side,  where  the  same  operation 
is  repeated,  the  boring  being  here  carried  to  size  for  grinding.  This 
rotating  of  the  table,  in  turn,  brings  a  new  set  of  the  cylinders  up  to 
be  rough-bored.  The  process  is  continuous,  the  work  being  removed 


20 


AV.  60— AUTOMOBILE  CONSTRUCTION 


from  the  finishing  side  and  new  cylinders  clamped  in,  while  the  rough 
boring  is  being  completed. 

For  setting  out  the  cutters  in  the  boring  bars,  the  construction 
shown  in  Fig.  16,  at  the  left,  is  used.  It  will  be  seen  that  a  taper- 
headed  screw  is  used  for  forcing  the  blades  out  simultaneously.  The 
cutters  B  bottom,  on  this  taper-headed  screw  C;  fillister  head  screws  D 
serve  to  keep  the  blades  forced  down  to  their  bearing  on  C,  and  so  draw 
them  firmly  against  the  side  of  the  slot.  By  this  means  two  or  more 
blades  may  be  set  out  simultaneously  for  regrinding  to  exact  size. 
A  similar  arrangement  (see  view  at  the  right  of  Fig.  16)  is  used  for 
cutters  in  the  middle  of  long  boring  bars,  except  that  the  taper  point 
of  a  screw  tapped  into  the  bar  from  the  side,  is  used  in  place  of  the 
corresponding  taper-headed  screw  in  the  first  case. 


ADJUSTMENT  FOR 
END  CUTTERS 


ADJUSTMENT  FOR 

CUTTERS  IN  CENTER 

OF  BAR 

Machinery,  .\.X 


Fig.  16.     Adjustment  used  for  Boring-bar  Blades 

The  bore  of  these  cylinders  is  finished  in  Heald  internal  grinding 
machines  especially  built  for  this  work.  These  are  of  the  type  in  which 
the  work  remains  stationary  while  the  axis  of  the  spindle  is  revolved 
about  the  center  line  of  the  bore  and  parallel  with  it,  on  such  a  diam- 
eter as  to  bring  the  outer  periphery  of  the  wheel  in  contact  with  the 
inner  surface  of  the  bore.  The  grinding  spindle  is  fed  out  so  as  to 
rotate  in  a  larger  circle  as  the  diameter  of  the  bore  is  increased.  An 
interesting  feature  shown  in  Fig.  15  is  the  provision  of  a  flexible  suc- 
tion tube  for  drawing  out  the  dust  of  the  grinding  through  the  inlet 
and  exhaust  ports,  and  also  the  provision  made  for  water  cooling. 
The  water  is  not  applied  directly  to  the  wheel,  as  in  an  ordinary 
external  grinder,  but  is  forced  instead  through  the  regular  water 
jacket  of  the  cylinder  casting.  This  reproduces,  in  a  measure,  the  con- 
ditions met  with  in  actual  use,  and  so  tends  toward  accurate  work. 

Machines  and  Fixtures  for  Grinding-  and  Lapping- 
There  are  other  operations  of  interest  in  the  grinding  department 
besides  that  of  finishing  the  bore  of  the  cylinders.  Extensive  use  is 
made  of  the  Pratt  &  Whitney  face  grinding  machine  for  finishing  flat 
-nrf;t<M's:  in  fact,  it  lias  largely  displaced  the  vertical  milling  machine 
for  this  work,  on  parts  in  which  the  surface  to  be  finished  is  clear  of 
projections  or  obstructions  to  the  sweep  of  the  wheel.  The  faces  of 


MANUFACTURING  METHODS 


21 


the  various  casings,  covers,  inlet  and  exhaust  pipes,  etc.,  are  finished 
on  this  machine.  In  the  past  most  of  these  parts  have  been  made  from 
castings  on  which  3-16-inch  of  stock  had  been  left,  in  accordance  with 
the  usual  practice  of  milling.  The  castings  come  true  enough  to  shape, 
however,  to  permit  of  this  finish  being  reduced  to  1-16  of  an  inch,  or 


Fig.  17.     The  Acme  of  Simplicity  in  Fixture  Making.     Face  Grinding 
the  Steering  Gear  Casing 


Fig.  18.     Grinding  the  Bore  of  the  Cams  Concentric  with 
the  Cylindrical  Surface 

thereabout,  when  finished  by  grinding,  thus  materially  reducing  the 
time  required.  Even  when  removing  3-16-inch  of  stock  the  grind- 
ing machine  has  proved  its  superiority  to  the  milling  machine  in  the 
matters  of  cost,  finish  and  accuracy.  The  foreman  of  the  grinding 
department  discovered  that  a  little  experimenting  and  investigating 
along  the  line  of  the  grading  of  wheels  made  a  tremendous  difference 


22  No.  60— AUTOMOBILE  CONSTRUCTIOX 

in  their  durability  and  effectiveness  in  removing  metal.  For  aluminum 
work  a  vitrified  carborundum  wheel  of  about  No.  24  grain  and  grade 
H  hardness  is  used,  a  soda  compound  being  employed  for  cooling. 

The  cover  side  of  the  steering  gear  casing  is  one  of  the  parts  sur- 
faced on  the  face  grinder.  An  exceedingly  simple  fixture  is  used  for 
holding  it.  This  fixture,  as  may  be  seen  in  Fig.  17,  is  nothing  more 
or  less  than  a  mass  of  lead  melted  and  poured  around  a  sample  casting 
as  a  form.  The  work  is  set  into  the  bed,  thus  prepared  to  receive 
it,  and  is  supported  on  the  table  by  its  own  weight,  no  fastening  being 
uecessary.  The  castings  come  uniform  enough  so  that  they  fit  well 
in  this  device,  except  at  certain  points  around  the  gates  and  sprues, 
where  it  is  found  necessary  to  relieve  the  form  slightly  to  allow  for 
these  variations.  It  may  be  mentioned  that  the  other  or  main  member 
of  the  steering  gear  casing  has  a  boss  projecting  above  the  finished 


GUIDE  SURFACE 


TABLE  OF  PROFILER 

Fig.  19.    The  Simplest  and  Stiffest  Arrangement 
for  Cam  Cutting 

surface  of  the  joint,  making  it  necessary  to  mill  that  surface.  The 
joint  is  thus  formed  of  one  ground  and  one  milled  surface. 

In  Fig.  18  is  shown  the  operation  of  grinding  the  holes  in.  the  cams. 
It  is  quite  important  that  the  cylindrical  portion  of  the  cam  shall 
be  exactly  concentric  with  the  cam-shaft  to  prevent  shock  or  jar  during 
the  period  "when  the  valves  are  supposed  to  be  closed.  To  make  sure 
that  this  surface  is  concentric,  the  cam  is  located  by  it  in  the  grinding 
fixture  as  shown.  After  the  fixture  has  been  mounted  on  the  faceplate 
of  the  machine,  the  gripping  surfaces  of  the  two  jaws  at  the  right  are 
ground  out  by  the  internal  grinding  attachment,  to  the  radius  of  the 
cydindrical  dwell  of  the  cam.  The  cam  is  clamped  against  the  surface 
thus  prepared,  by  the  lever,  which  forces  a  wedge  across  and  down 
upon  the  cam,  holding  it  firmly  into  the  corner  in  both  directions. 

It  will  be  seen  that  this  car  does  not  employ  the  integral  cam-shaft. 
By  giving  careful  attention  to  the  locating  of  the  cams  on  the  shaft 
and  by  being  careful  to  obtain  a  strong  drive  fit  between  them,  the 
difficulties  of  loosening  and  dislocation,  which  the  integral  construc- 
tion is  expected  to  cure,  have  been  avoided.  It  is  thus  permitted  to 
cut  the  cams  in  a  way  which  gives  the  best  chance  for  producing  accur- 
ate shapes  and  smooth  finish.  The  obvious  scheme  shown  in  the 


MANUFACTURING  METHODS 


23 


sketch,  Fig.  19,  is  followed,  the  operation  being  performed  on  a  profiling 
machine.  The  connection  between  the  forming  cam  and  the  work  is 
so  close  that  the  difficulties  of  springing  and  chattering,  met  with  in 
the  construction  of  the  more  elaborate  machines  required  for  integral 
cam-shafts,  are  avoided. 

Another  faceplate  fixture  for  internal  grinding  is  shown  in  Fig.  20, 
where  it  is  employed  for  grinding  the  hole  in  the  hardened  nickel 
steel  sockets  used  for  the  universal  joints  (see  Fig.  7,  Chapter  I). 
The  socket  is  held  in  the  same  way  as  when  in  use,  by  a  nut  screwed 
onto  its  threaded  shank.  It  is  also  located  in  the  same  way,  a  pin  in 
the  fixture  engaging  a  slot  in  the  flange  as  shown.  A  limit  of  0.0005 


Fig.  2O.     Grinding  the  Holes  in  the  Universal  Joint  Pivots 

inch  only  is  permitted  in  this  operation, :  and  an  allowance  of  about 
0.003  inch  for  the  depth  of  the  hole  is  the  maximum,  just  enough  being 
permitted  for  proper  lubrication  by  the  grease  supply  provided.  This 
fixture  is  kept  in  place  on  the  machine  practically  throughout  the 
season.  If  at  any  time  it  is  necessary  to  remove  it,  however,  it  can 
again  be  trued  up  by  clamping  a  model  socket  in  place,  inserting  a 
plug  in  the  ground  hole,  and  truing  up  the  plug.  These  studs  are 
held  in,  the  same  way  in  the  screw  machine  for  roughing  out  the  hole 
preparatory  to  grinding.  The  form  of  internal  grinding  spindle  used 
should  be  noted.  One  of  them  is  shown  detached  in  Fig.  18,  lying  on 
the  table  of  the  machine.  These  spindles  and  their  bearings  are  self- 
contained,  interchangeable  and  adapted  to  work  in  holes  of  various 
sizes.  The  clutch  drive  provided  rotates  the  spindle  without  side  pres- 
sure on  the  bearings. 

Machining-  the  Members  of  the  Squared  Drive 

As  previously  mentioned,  the  use  of  keys  is  eliminated  in  the  drive 
of  the  Stevens-Duryea  machine,  their  place  being  taken  by  square 
sockets  throughout.  A  tapered  square  drive  is  used  to  connect  the 


24  Xo.  60— AUTOMOBILE  CONSTRUCTION 

crank-shaft  with  the  driving  member  of  the  clutch.  The  method  of 
machining  this  is  shown  in  Fig.  21.  It  has  been  found  advisable  to 
keep  the  milling  machine  set  up  for  this  work,  continuously,  owing 
to  the  difficulty  of  making  a  good  taper  square  fit.  When  the  machine 
has  once  been  set,  it  is  kept  so  throughout  the  season.  An  ordinary 
dividing  head  is  used,  as  shown,  tipped  up  to  the  angle  of  the  taper. 
To  the  faceplate  of  this  dividing  head  is  clamped  the  fly-wheel  flange 
of  the  crank-shaft.  The  outer  end  of  the  crank-shaft  is  supported  in  a 
suitable  steady-rest  as  shown.  For  shorter  lengths  of  crank,  filling 
pieces  are  employed,  having  flanges  bolted  to  the  faceplate  at  one  end, 
and  to  the  work  at  the  other.  The  use  of  filling  pieces  permits  machin- 
ing of  the  full  line  of  crank-shafts  without  disturbing  the  adjustments. 


Fig.  21.    A  Vertical  Milling  Machine  set  up  for  Milling  the  Tapered 
Square  Drive  on  the  Crank- shaft 

The  automatic  cross-feed  is  employed  in  feeding  the  work  past  the 
end  mill  in  the  vertical  milling  attachment.  Tne  table  has  to  be  so 
far  overhung  that  an  out-board  support  is  provided  as  shown,  which 
permits  this  cross-feed.  This  consists  of  a  sliding  guide,  supported  by 
two  standards,  reaching  to  the  floor  and  provided  with  jack  screw 
adjustments  for  careful  leveling. 

The  squared  holes  of  the  drive  are  finished  on  a  La  Pointe  broaching 
machine  in  the  usual  manner.  The  further  machine  shown  in  Fig. 
23  is  engaged  in  finishing  taper  square  holes  in  the  clutch  driving 
flange,  this  being  the  member  into  which  the  taper  squared  end  of  the 
crank-shaft  shown  in  Fig.  21  fits.  The  hole  is  first  reamed  out  to  a 
taper  a  little  larger  than  the  distance  across  the  flat  of  the  finished 
hole.  The  work  is  then  mounted  on  a  broaching  machine  on  the  fix- 
ture shown  in  place.  As  may  be  seen,  the  broach  cuts  one  corner  of 
the  square  hole,  and  one-half  way  up  each  of  the  two  adjacent  sides, 
into  the  relief  formed  by  the  taper  hole.  A  dog  is  fastened  to  the  hub 
of  the  work,  and  the  latter  is  mounted  on  a  taper  plug  fitting  the  hole, 
with  the  tail  of  the  dog  located  by  a  pin  in  the  faceplate  of  the  fixture, 


MANUFACTURING  METHODS 


25 


the  latter  being  mounted  on  the  faceplate  of  the  machine  at  an  angle 
as  shown,  to  agree  with  the  angle  of  the  corner  of  the  tapered  sides. 

One  pass  of  the  broach  finishes  one  corner  of  the  tapered  hole.  The 
broach  is  then  returned  to  the  starting  position,  the  work  is  drawn  off 
the  taper  plug,  the  dog  indexed  to  the  second  pin  on  the  faceplate, 
the  work  is  put  in  position  and  the  second  corner  broached.  This 
operation  is  repeated  until  the  four  corners  have  been  machined,  and 
the  square  hole  finished,  the  work  being  centered  on  the  taper  plug  of 
the  fixture  throughout  the  whole  operation.  A  taper  square  gage  is 
shown  lying  on  top  of  the  broach  in  the  engraving.  This  is  used  for 
testing  the  fit  of  the  holes  and  the  accuracy  of  the  work,  and  a  most 
accurate  fit  is  made  on  this  by  no  means  easy  operation.  In  the 
machine  in  the  foreground,  another  operation  is  being  done — that  of 


FACE  PLATE  OF  BROACHING  MACHINE 


SIZING  TOOL,  WITH  SUCCESSIVELY 
LARGER  BEADS 


Fig.  22.     Method  of  Sizing  Phosphor-bronze  in  the  Broaching 
Machine  by  Compression 

broaching  the  driving  slots  in  the  driving  clutch  members  for  the  mul- 
tiple disks. 

Sizing-  Round  Holes  in  the  Broaching-  Machine 

Another  unusual  operation  for  which  the  broaching  machine  is  here 
used,  is  that  of  sizing  holes  in  hard  phosphor-bronze  bushings.  This 
material,  as  any  mechanic  who  has  had  any  experience  with  it  knows, 
is  as  hard  on  a  finishing  reamer  as  anything  well  can  be.  It  is  tough, 
elastic  and  slippery,  and  the  less  there  is  to  ream  the  more  difficult 
becomes  the  operation.  Instead  of  reaming  such  holes,  the  tools  shown 
in  Fig.  22  are  used  in  this  shop.  It  will  at  once  be  seen  that  the  opera- 
tion is  that  of  compressing  the  metal  in  the  sides  of  the  hole,  until  it 
has  been  enlarged  to  the  finished  size.  The  tool  is  drawn  through 
the  work.  Each  of  the  rounded  rings  or  beads  is  a  little  larger  than 
its  predecessor,  thus  gradually  compressing  the  metal  the  desired 
amount.  The  finished  hole  springs  to  a  size  smaller  by  some  few 
thousandths  than  the  diameter  of  the  largest  ring  on  the  tool,  so  that 
the  size  of  the  latter  has  to  be  determined  by  experiment.  This  allow- 
ance varies  slightly  also,  as  may  be  imagined,  with  the  thickness  of 
the  wall  of  metal  being  pressed.  In  such  a  part  as  that  shown  in  Fig. 
22,  for  instance,  after  drawing  through  the  sizing  tool  in  the  broach- 
ing machine,  it  will  be  found  that  the  hole  will  be  somewhat  larger  in 
the  large  diameter  of  the  work  than  in  the  hubs.  It  has  been  found 
that  this  difference  in  size  can  be  practically  avoided  by  passing  the 


26 


No.  60— AUTOMOBILE  CONSTRUCTION 


sizing  tool  through  the  work  three  or  four  times.  Few  pieces  of  this 
kind  are  found,  however.  The  operation  is  a  rapid  one  as  compared 
with  reaming. 

An  Adaptable  Lapping  Machine 

The  machine  shown  in  Fig.  24  was  built  mainly  in  the  factory,  use 
being  made,  however,  of  the  adjustable  columns  of  a  Taylor  &  Fenn 


Fig.  23.    A  Set  of  Interesting  Broaching  Operations 


Fig.  24.    Machine  for  Circular  and  Square  Lapping  Operations 

sensitive  drill  press.  This  special  machine  is  intended  for  lapping 
out  the  square  holes  of  the  drive,  but  is  provided  also  with  a  rotary 
movement  in  addition  to  the  vertical  movement  thus  necessary,  so  as 
to  provide  for  cylindrical  lapping  as  well.  The  driving  pulley  at  the 
right  gives  the  reciprocating  motion,  while  the  pulley  at  the  left 
rotates  the  spindles  through  the  medium  of  the  regular  geared  speed 


MANUFACTURING  METHODS  27 

drive.  The  sprocket  wheels  shown,  driven  from  the  right,  are  loose 
on  the  driving  shaft,  and  carry  eccentrics  whose  rods  are  extended  to 
form  racks  engaging,  through  a  suitable  clutch  connection,  the  pinion 
shafts  by  which  the  spindle  quills  are  fed  up  and  down.  It  is  thus 
possible  to  give  a  rotating  and  reciprocating  movement  to  the  spindles, 
either  together  or  separately. 

Separating-  Piston  Ring's 

Another  milling  operation  is  shown  in  Fig.  25.  It  is  a  common 
practice  to  make  piston  rings  on  an  automatic  machine  specially 
rigged  up  for  the  purpose,  separating  the  rings  from  the  finished 
casting  by  means  of  a  series  of  parting  or  cutting  off  tools,  each  of 


Fig.  25.     Cutting  out  Piston  Rings  in  the  Vertical  Milling  Machine 

which  is  set  a  little  in  advance  of  the  other  so  that  the  rings  will 
cut  off  in  regular  succession.  The  parting  tool,  however,  especially 
when  used  in  severing  cast  iron  work  like  this,  having  an  eccentric 
bore,  leaves  a  considerable  burr.  In  the  method  of  severing  the  rings 
shown  here,  the  eccentric  cylinder  is  first  finished  complete  on  the 
turret  machine.  Then  it  is  mounted  on  an  internal  expansion  chuck 
on  the  faceplate  of  the  cylindrical  attachment  of  the  Becker  vertical 
milling  machine,  as  shown.  This  chuck  is  provided  with  clearance 
grooves  for  the  gang  of  saws  shown  in  the  engraving.  These  are  sunk 
into  the  cylinder,  and  then  the  work  is  rapidly  revolved,  cutting  out 
the  eight  rings  at  once.  The  saws  are  permanently  mounted  on  their 
arbor,  with  separating  collars  ground  to  the  proper  thickness. 

Examples  of  Fixtures  Used  for  Drill-press  Operations 

The  drilling  department  seems  unusually  small,  when  compared 
with  the  size  of  the  whole  plant,  and  gives  the  appearance  of  being 
worked  at  high  pressure.  The  large  output  required  is  evidently 
maintained  by  the  universal  use  of  highly  developed  jigs  for  all 


28  No.  60— AUTOMOBILE  CONSTRUCTION 

manufacturing   operations.     Multiple   spindle    drill    presses    are    used 
to  almost  the  entire  exclusion  of  the  single  spindle  type. 

Fig.  26  Is  interesting  as  showing  the  development  of  the  jig  for  a 
comparatively  simple  operation — that  of  drilling  the  cotter  pin  hole 
in  a  headed  cylindrical  stud.  In  the  first  apparatus  employed  (not 
shown)  the  stud  was  pushed  into  a  hole  up  to  its  head,  and  held 
there  by  a  lever,  one  piece  being  done  at  a  time.  This  rigging  had 
two  faults.  One  piece  at  a  time  is  held,  and  trouble  with  chips  and 
burrs  was  experienced,  as  might  be  imagined.  An  improvement  on 
this  device  is  shown  in  the  two  jigs  at  the  right,  where  a  base  with 
a  set  of  V's  is  provided  in  which  several  of  the  pins  may  be  placed, 
their  heads  being  pressed  up  against  the  end  of  the  V-block  by 


Fig.  26.    Interesting  Drill  Jig's  for  a  Simple  Operation 

springs.  The  cover  being  clamped  down  on  the  work,  the  parts  are 
thus  held  for  the  drilling  operation.  This,  however,  was  not  quite 
easy  enough  to  clean  to  suit  the  ideas  of  the  tool  designer,  so  the 
fixture  shown  at  the  left  was  used  for  the  next  tool  of  tnis  kind  that 
had  to  be  made.  Here  hinged  sides  are  used  instead  of  springs  as 
in  the  previous  case.  These  sides  fold  up  and  press  the  heads  of  the 
work  against  the  edges  of  the  V-block.  When  they  are  turned  down 
and  the  cover  of  the  V-block  is  raised,  the  top  surface  of  the  V-block 
is  all  clear,  so  that  the  presence  of  chips  shows  inexcusable  careless- 
ness on  the  part  of  the  operator.  When  the  sides  are  folded  up  against 
the  work  and  the  cover  is  brought  down,  the  latter,  by  means  of 
wedge"  surfaces,  presses  the  sides  in,  holding  the  heads  of  the  work 
firmly  in  place  and  clamping  them  down  on  the  V-block  at  the  same 
time. 

The  jig  shown  at  work  in  Fig.  27  is  used  for  drilling  and  reaming 
the  connecting-rod  holes.  It  is  of  the  "four-legged  table"  variety,  with 
suitable  clamps  and  hook  bolts  for  taking  the  strain  of  the  cut  with- 
out permitting  noticeable  deflection  and  consequent  inaccuracy  in  the 


MANUFACTURING  METHODS 


29 


work.  A  feature  of  the  construction  which  is,  perhaps,  old  enough, 
but  probably  new  to  many,  is  the  provision  made  for  both  drilling  and 
reaming  with  a  fixed  bushing,  thus  avoiding  the  use  of  slip  bushings 
of  different  diameters.  For  drilling,  the  jig  is  used  as  shown  in  the 
engraving,  with  the  work  clamped  beneath  the  plate  and  the  jig  bush- 


.  27.    Gang  Drill  used  in  Drilling  and  Reaming 
Connecting-rod  Ends 


Fig.  28.    An  Unusual  Array  of  Automatic  Chuckinar  Machines ; 
Thirty-one  are  used  in  this  Department 

ings  above,  guiding  the  drills.  Fpr  reaming,  the  jig  is  reversed  and 
a  reamer  is  used  having  a  pilot,  which  passes  through  the  work  into 
the  jig  bushing  (now  on  the  under  side  of  the  plate)  by  which  it  is 
guided. 

Fig.  28  shows  what  is  by  long  odds  the  largest  aggregation  of  auto- 
matic chucking  machines  the  writer  has  ever  seen.     There  are  thirty- 


30 


60— AUTOMOBILE  CONSTRUCTION 


one  of  the  Potter  &  Johnston  type.  Practically  every  turned  part  not 
made  in  the  screw  machine  from  the  bar  is  produced  on  these  ma- 
chines. That  old  standby,  the  engine  lathe,  appears  to  be  about  the 
rarest  machine  tool  in  the  shop. 

Fig.  29  shows  a  section  of  the  engine  assembling  room.     It  will  be 
noted  that  machine  tools  are  few  and  far  between,  the  only  ones  in 


Pig.  29 


Engine  Assembling  Department 


sight  being  a  drill  press,  speed  lathe,  and  two  or  three  grinding  stands 
for  sharpening  tools.  This  shows  that  the  manufacturing  operations 
have  been  performed  with  great  exactness.  The  question  of  assembly 
is  simply  one  of  bolting  and  screwing  the  separate  parts  together. 
The  engines  here  shown  are  of  the  four-  and  six-cylinder  type.  The 
overhead  trolley  lines  should  be  noted. 


CHAPTER  III 


MANUFACTURING  AUTOMOBILE 
EQUALIZING  GEARS* 

The  present  chapter  deals  with  operations  which  do  not  present 
any  especially  unusual  or  spectacular  features,  yet  they  have  a  valne 
derived  from  the  fact  that  they  are  closely  related  to  the  operations 
which  produce  the  bulk  of  the  product  of  the  machine  shops  of  the 
country;  for  that  reason  they  should  attract  the  attention  of  mechanics 
interested  in  accurate  and  economical  work.  The  operations  for  mak- 
ing a  complete,  compact  machine  unit — a  differential  or  equalizing  gear 
for  automobile  use,  is  described  from  beginning  to  end.  The  com- 
pleteness of  the  job  gives  it  a  suggestive  value  that  would  not  be 


Fig.  3O.    The  Equalizing  Gear  Complete,  with  Bevel  Gear  and  Pinion 

offered  by  a  series  of  miscellaneous  operations,  however  interesting.' 
The  value  of  this  description,  however,  does  not  depend  on  its  com- 
pleteness alone,  as  many  of  the  specific  shop  operations  give  evidence 
of  a  high  degree  of  manufacturing  ability. 

Description  of  the  Equalizing1  Gear 

Figs.  30,  31  and  32  show  assembled,  dismantled  and  detail  views, 
respectively,  of  an  equalizing  or  differential  gear,  designed  by  Mr.  A.  A. 
Fuller,  of  the  Providence  Engineering  Works,  Providence.  R.  I.  The 
determining  feature  of  this  design  is  the  necessity  for  getting  a  maxi- 
mum of  strength  and  effectiveness  in  a  minimum  of  space — coupled, 


*  MACHINERY,  December,  1909. 


32 


No.  60— AUTOMOBILE  CONSTRUCTION 


of  course,  with  reasonable  cost  of  manufacture.  This  problem  was 
attacked  by  scientific  analysis.  It  was  possible,  without  great  diffi- 
culty, to  obtain  reasonable  strength  in  the  casing  which  contains  the 
equalizing  gearing.  The  crucial  point  was  in  the  design  of  the  equal- 
izing gears  themselves.  In  determining  the  proportions  of  the  gears, 
curves  were  drawn  showing  the  strength  of  the  teeth  for  lay-outs  of 
varying  pitch  and  number  of  teeth,  arranged  to  be  contained  within 
a  casing  of  a  given  diameter.  The  strength  and  bearing  area  of  the 
pivots,  and  the  strength  of  the  pinions  as  limited  by  the  thickness 
of  the  shell  between  the  bottom  of  the  tooth  and  the  bore,  had  also  to 
be  reckoned  with.  The  tooth  shapes  were  not  confined  to  standard 
forms,  but  various  pressure  angles  and  heights  of  addendum  were 


Fig.  31.    A  Small  Size  of  Equalizing  Gear  Dismantled 
to  show  Construction 

investigated.  By  comparing  the  curves  for  various  possible  designs, 
a  certain  pitch,  number  of  teeth  and  shape  of  tooth  for  the  various 
gears  were  found  for  each  diameter  of  casing,  so  proportioned  that 
if  any  of  the  dimensions  were  changed,  the  mechanism  became  weaker 
•  instead  of  stronger.  These  proportions,  worked  into  a  design  satis- 
factory in  other  particulars,  have  been  adopted  as  standard,  and  the 
makers  feel  confident  that  it  is  impossible  to  enclose  in  the  same 
space  gears  of  greater  strength  than  they  are  offering  in  the  design  illus- 
trated herewith.  As  this  confidence  is  based  on  mathematical  calcu- 
lations and  has  been  further  tested  by  many  months  of  experiein •• .-.  it. 
seems  reasonable  that  they  should  hold  to  it. 

Referring  particularly  to  Fig.  32,  the  mechanism  is  contained  within 
case  B  and  covers  A  and  A'.  It  revolves  in  the  rear  axle  gear  casing 
on  ball  bearings,  mounted  at  the  ends  of  casings  A  and  A',  and  the 
driving  bevel  gear  is  carried  on  the  periphery  of  case  B,  to  which  it 
is  clamped  by  hexagon-head  screws  H.  The  pivots  E  are  riveted  into 


MAKING  EQUALIZING  GEARS 


33 


the  flanges  of  covers  A  and  A',  three  in  one  side  and  three  in  the  other. 
These  pivots  carry  pinions  F  and  F'  meshing  with  gears  C  and  C";  the 
latter  run  in  bronze  bushings  D  and  D'  forced  into  the  two  covers,  and 
are  provided  with  broached  square  holes  by  which  the  floating  wheel 
shafts  are  driven.  As  will  be  seen  in  Fig.  31  in  connection  with 
Fig.  32,  gear  C  meshes  with  pinion  F\  which  also  meshes  with  pinion 
F,  the  latter  in  turn  engaging  gear  C".  Thus,  when  gear  C  is  turned, 
gear  C'  is  revolved  in  the  opposite  direction,  and  vice  versa,  thus  form- 
ing a  spur  gear  differential  mechanism. 

Attention  may  be  called  to  some  of  the  features  which  make  for 
strengtlj.  in  this  design.  It  will  be  seen,  for  instance,  that  the  gears 
have  teeth  of  special  shape  and  of  very  coarse  pitch  and  few  numbers 
of  teeth.  The  pinions  have  eight  teeth  and  the  gears  sixteen  each.  In 


Fig.  32.     Details  of  Construction  of  the  7-inch  Equalizing-  Gear 

designing  the  mechanism  .by  analysis,  as  described,  it  was  found  that 
this  construction  was  necessary  for  strength.  Older  designs  of  this 
kind,  more  commonly  met  with,  in  which  the  pinions  are  smaller  in 
proportion  to  the  gears,  have  repeatedly  proved  their  weakness  by 
breakage. 

Mention  should  also  be  made  of  the  solid  way  in  which  the  parts 
composing  the  casing  are  fastened  together.  The  casing  B  is  provided 
with  tongues  locking  into  the  grooves  cut  in  covers  A.  so  that  the  strain 
of  transmission  is  taken  on  these  interlocking  members  and  is  not 
taken  by  the  bolts,  dowel  pins  or  similar  parts.  So  far  as  this  tor- 
sional  strain  is  concerned,  the  casing  is  as  strong  as  if  it  were  made 
of  solid  metal — an  impossible  construction,  of  course.  Through  bolts 
and  nuts  G  and  G'  clamp  the  whole  casing  firmly  together. 

The  proper  meshing  of  the  bevel  gears  can  be  controlled  by  shifting 
the  whole  casing  axially  in  its  bearings.  Nuts  are  mounted,  for  this 
purpose*  one  on  the  threaded  diameter  of  A  and  the  other  at  the  same 
point  on  A'.  By  loosening  one  and  tightening  the  other  the  teeth  of  the 
gears  can  be  brought  more  closely  into  contact,  or  vice  versa. 

The  provisions  for  oiling  should  be  noted.  The  casing  on  the  rear 
axle  is  provided  with  a  bath  of  oil  in  which  the  bevel  gears  run.  Three 


34  No.  60— AUTOMOBILE  CONSTRUCTION 

holes  cut  in  the  exterior  of  B  (not  shown  in  Fig.  31,  but  visible  in  the 
detail  views  of  the  operations  in  Fig.  33,  and  at  the  right  of  Fig.  34, 
where  these  holes  are  being  drilled)  admit  oil  from  this  bath  into  the 
interior  spur  gears.  Pivots  E  and  pinions  F  are  grooved,  as  are  also 
gears  C  and  C'  permitting  a  flow  of  oil  through  the  whole  structure,  kept 
in  constant  motion  through  the  revolving  of  the  parts. 

In  describing  the  manufacture  of  this  device  we  will  take  up  each 
part  in  turn.    The  manufacture  of  the  bevel  gears  will  not  be  described 


Fig.  33.    Milling  the  Drive  Tongues  In  the  Gear 
Case— Second  Operation 

in  detail,  as  their  design  is  determined  by  the  maker  of  the  car  in  which 
the  device  is  to  be  installed.  The  first  part  to  be  considered  will  be 
the  gear  case,  shown  at  B  in  Fig.  32. 

Operations  in  the  Manufacture  of  the  Gear  Case 

The  case  is  made  from  a  malleable  iron  casting  on  which  tin1  first 
operation,  naturally,  is  that  of  snagging  to  remove  fins,  gates,  etc.  The 
second  operation  is  performed  in  the  Jones  &  Lamson  flat  turret  lathe, 
of  which  large  use  is  made  in  this1  shop.  The  casting  is  placed  in  the 


MAKING  EQUALIZING  GEARS  35 

chuck  of  the  machine  with  the  flange  outward.  In  this  operation  the 
hole  is  finished  to  size,  the  flange  is  turned,  and  the  projecting  end  is 
faced.  The  regular  equipment  is  used  for  this  purpose,  the  only  special 
tools  being  gages  for  the  inside  diameter  of  the  hole  and  the  outside 
diameter  of  the  flange. 

In  the  third  operation,  performed  in  the  same  machine,  the  part  is 
grasped  by  the  finished  flange  in  special  soft  chuck  jaws,  which  have 
been  turned  in  place  to  fit  the  diameter  they  are  to  receive.  This  givea 
assurance  that  the  work  done  in  this  operation  will  be  true,  within 
reasonable  limits,  with  the  cuts  previously  taken.  Regular  flat  turret 
lathe  equipment  is  used  for  this  operation  as  well,  suitable  gages  of 


Fig.  34.    Drilling  the  Three  Oil  Supply  Holes  in  the  Case  (see  Fixture  at 
the  Right),  and  Drilling  the  Bolt  and  Pivot  Holes  in  the  Cover 

simple  construction  being  provided.  The  next  operation,  shown  at  the 
right  of  Fig.  34,  is  drilling  the  three  holes  which  admit  oil  to  the  inter- 
ior of  the  case.  This  jig  is  of  the  simplest  possible  construction,  con- 
sisting of  a  knee  with  a  turned  seat  on  which  the  work  is  placed,  and  an 
overhanging  lug  carrying  a  drill  bushing.  A  clamp  provides  for  holding 
the  work,  and  a  plug,  entering  a  suitably  located  hole  in  the  seat,  pro- 
vides means  for  indexing  the  second  and  third  holes  drilled,  from  the 
one  previously  completed.  The  other  operation  shown  in  this  engrav- 
ing will  be  described  later  on. 

The  tongues  which  interlock  with  the  grooves  in  covers  A  and  A'  (see 
Fig.  32)  have  next  to  be  milled.  The  fixture  for  doing  this  is  shown 
in  use  in  Fig.  33.  It  consists  of  a  base  provided  with  an  index  plate  and 
a  revolving  table,  by  means  of  which  the  work  may  be  indexed  step  by 
step  to  cut  the  various  tongues.  These  are  shaped  by  straddle  mills 
which  form  the  opposite  sides  of  the  tongues  parallel,  so  that  they  fit 
into  corresponding  grooves  milled  into  the  covers  by  a  straight-sided 
cutter.  In  the  operation  illustrated,  tongues  have  been  cut  on  one  side 


36 


No.  60— AUTOMOBILE  CONSTRUCTION 


of  the  casing,  which  is  located  in  its  seat  in  the  fixture  by  the  inter- 
locking of  these  tongues  with  grooves  provided  to  receive  them  as 
shown.  This  assures  alignment  of  the  cuts  on  each  edge  of  the  case.  In 
the  first  operation  the  uncut  edge  of  the  work  is  simply  set  down  onto 


Fig.  35.    The  First  Turret  Lathe  Operation  in  Finishing  the  Gear  Case  Covers 


Fig.  36.    Second  Operation  on  the  Flat  Turret  Lathe  using  Special  Jaws 

this  seat.  It  is  held  down  by  three  clamps,  provided  with  noses  which 
enter  the  three  holes  drilled  to  admit  oil  to  the  interior  of  the  mechan- 
ism. 

It  is  interesting  to  see  the  expertness  with  which  the  operator  cuts 
cut   these   tongues.     The   automatic   feed    is   set  at  the   highest   point 


MAKING  EQUALIZING  GEARS 


37 


practicable  when  cutting  the  full  depth.  As  this  would  be  less  than 
the  maximum  possible  when  the  cutter  is  entering  the  work,  he  begins 
with  a  hand-feed  at  a  considerably  higher  rate,  throwing  in  the  auto- 
matic feed  when  the  cutter  gets  down  to  work.  Although  the  machine 
is  of  modern  construction,  the  workman  feeds  in  all  the  belt  can 
handle.  The  gear  casing  is  now  complete  except  for  certain  opera- 
tions performed  on  it  in  assembling,  as  described  later. 

Operations  on  the  Gear  Case  Cover 

The  gear  case  covers  are  made  from  machine  steel  drop  forgings. 
After  the  snagging,  the  first  operation  is  the  simple  one  of  putting 
a  1^-inch  hole  through  the  center  of  the  forgings.  This  is  a  drill 
press  operation  and  is  merely  done  to  remove  stock,  it  being,  of 


Fig.  37.     Layout  of  Tools  on  the  Flat  Turret  Lathe  for  the 
Operation  shown  in  Fig-.  35 

course,  impracticable  to  form  the  hole  in  the  forging.  It  is  next 
clamped  by  the  rim  with  the  hub  projecting,  in  the  chuck  of  the  flat 
turret  lathe.  This  first  turret  lathe  operation  is  shown  in  Figs.  35 
and  37,  the  latter  diagram  indicating  the  arrangement  of  the  tools. 

The  first  cut  is  shown  at  A.  An  outside  turning  and  boring  tool, 
acting  in  conjunction,  rough  turns  the  hub  and  rough  bores  the  hole. 
At  the  next  station,  B,  three  tools  simultaneously  face  the  end  of  the 
hub  and  the  two  surfaces  of  the  flange.  Two  cuts  are  taken  with 
these,  one  for  roughing  and  one  for  finishing.  A  third  cut  is  taken 
with  the  same  tools  fed  axially  against  the  work  to  form  the  two 
grooves  in  the  face  of  the  flange,  as  most  plainly  shown  in  Fig.  32. 
At  the  third  station  (7,  another  turning  tool  removes  the  stock  on  two 
diameters  of  the  hub,  two  cuts  being  taken.  At  D  a  finishing  cut  is 
taken  over  the  smaller  diameter,  while  at  E  a  form  tool  shapes  that 
portion  of  the  hub  extending  from  the  threaded  diameter  to  the  flange. 
This  operation  is  completed  in  about  18  minutes. 


33  No.  60— AUTOMOBILE  CONSTRUCTION 

In  the  second  operation  (see  Figs.  36  and  38),  the  completed  end 
of  the  piece  is  grasped  in  soft  jaws  turned  to  fit  the  surface  they  grasp, 
assuring  true  running  of  the  surfaces  made  in  the  two  operations. 
The  tool  at  A  bores  out  the  large  diameter  of  the  hole,  which  is  for 
clearance  only.  The  reamer  at  B  finishes  the  small  diameter  to  size. 
The  tool  at  C  faces  the  flange,  taking  two  cuts,  one  to  rough  out 
stock  and  the  second  to  bring  it  to  size.  A  flat-nosed  tool  at  D  finishes 
the  flange.  The  tool  at  E  roughs  out  the  counterbore,  while  that  at 
F  finishes  it.  This  latter  tool  is  fed  directly  in,  boring  the  diameter 
of  the  counterbore  to  size  until  the  bottom  is  reached,  when  the  slid- 
ing head  is  fed  outward,  so  that  the  same  tool  faces  the  bottom  of 


Machinery,  X.T. 
Fig.  38.    Layout  of  Tools  in  the  Operation  shown  in  Pig.  36 

the  counterbore.  The  finishing  is  thus  done  by  turning  cuts  instead 
of  forming  cuts,  giving  a  higher  degree  of  accuracy.  Work  of  this 
kind  shows  the  flat  turret  lathe  to  very  good  advantage.  In  the  lay- 
out of  tools  shown  in  Figs.  37  and  38,  there  were  probably  no  special 
tools  of  any  kind  required,  with  the  exception  of  the  form  tool  E, 
the  rest  being  stock  turning  tools  of  the  kind  which  form  the  regular 
equipment  of  the  machine.  It  may  have  been  necessary  in  some 
cases  to  give  the  tool  a  knock  of  the  hammer  on  the  blacksmith's  anvil 
to  bend  it  in  one  direction  or  the  other,  but  nothing  more  would  be 
needed.  The  cross  sliding  head  and  the  multiple  stops  come  into 
play  in  such  operations  as  those  at  B  and  C  in  Fig.  37,  and  F  in  Fig. 
38,  giving  each  separate  tool  a  wide  range  of  usefulness,  especially 
when  it  is  so  made  that  it  can  be  used  for  both  turning  and  facing 
jobs. 

Of  course  there  are  all  sorts  of  opinions  about  such  matters,  but 
in   the   question  of    hand    i-cmitx    automatic    machines,    this    company 


MAKING  EQUALIZING  GEARS 


39 


believes  that  the  conditions  favor  the  use  of  the  hand  turret  lathe 
in  its  work.  The  simplicity  of  the  tolling  is  an  important  factor  on 
contract  work.  The  management  can  never  be  sure  of  the  long  con- 
tinuance of  any  job,  so  that  anything  approaching  costliness  or  elabor- 
ation is  prohibited.  Furthermore,  it  is  reasonably  certain  that  one 
hand  machine  will  turn  out  more  work  than  one  automatic,  particu- 
larly when,  as  in  this  shop,  there  is  an  inducement,  such  as  the 
premium  system,  for  the  workman  to  get  the  very  most  out  of  his 
machine.  He  is  constantly  changing  his  feeds  and  speeds  as  the 
varying  diameters,  depth  of  the  cut  and  condition  of  the  tool  require. 
He  is  thus  able  to  take  heavier  cuts  without  injuring  his  cutting 
edges  than  would  be  possible  without  constant  personal  supervision. 


Fig.  39.    Milling  the  Driving  Slots  in  a  Pair  of  Gear  Case  Covers 

Probably  three   or  four  changes  are  made  in  each  operation  to  one 
that  would  be  made  on  an  automatic  machine.    As  another  advantage, 
this   greater  production   of  the   machine   means   a  much   less   capital- 
outlay  per  dollar  of  output. 

It  certainly  does  keep  the  operator  busy  to  get  the  most  out  of  one 
of  these  lathes.  There  is  no  possibility  of  his  running  more  than  one 
machine,  on  this  particular  work  at  least.  Cuts  are  taken  very 
rapidly  and  changes  of  feed  and  speed  follow  each  other  in  constant 
succession.  There  is  a  line  of  demarkation  at  the  point  where  the 
intensity  of  production  on  the  part  of  the  hand  machine  and  the 
lower  capital  charge  on  machines,  buildings,  stock,  etc.,  balance  the 
higher  output  per  man  and  the  consequent  lessened  labor  cost  for  the 
automatic  machines.  In  accordance  with  their  judgment,  some  shop 
managers  will  draw  the  line  at  one  point  and  some  at  another.  It 
is  fortunate  for  the  builders  of  both  types  that  all  men  do  not  come  to 
the  same  conclusion  when  reasoning  from  the  same  premises. 


40 


No.  60— AUTOMOBILE  CONSTRUCTION 


In  Fig.  39  the  milling  machine  is  shown  rigged  up  to  cut  the  driving 
slots  in  a  pair  of  the  gear  case  covers.  The  two  are  mounted  together 
face  to  face  on  a  special  iron  arbor,  having  a  driving  tail  cast  integ- 
rally with  it  in  place  of  the  usual  separate  dog.  A  formed  cutter  is 
used  which  shapes  the  bottom  of  the  slot  to  the  true  radius  of  the 
inside  diameter  of  the  casing  B  (see  Figs.  32  and  33)  assuring  a  tight 
fit.  This  operation  and  that  shown  in  Fig.  33  have  to  be  done  to  close 
limits  with  good  indexing  plates,  only  0.001  inch  variation  being 
allowed  on  the  thickness  of  the  slot  and  the  tongue.  This  means 
that  in  order  to  make  a  good  fit  the  dividing  must  be  very  accurate. 
In  the  cases  the  writer  has  seen  assembled,  these  parts  drove  together 
with  a  very  little  gentle  urging  from  a  lead  hammer.  Not  much  of 


Fig.  4O.     Jig  for  Drilling  the  Bolt  and  Pivot  Holes  in  the  Gear  Case  Covers. 
Another  Jig  for  the  Same  Operation  is  shown  at  the  Left  of  Fig.  34 

anything  else  seemed  to  be  required.  In  Fig.  40  is  shown  a  jig  for 
drilling  the  bolt  and  pivot  holes  in  the  gear  covers.  It  is  of  simple 
construction,  the  cover  being  supported  on  four  legs  and  located  by 
a  central  spindle  over  which  it  is  dropped  and  by  which  it  is  clamped, 
an  open  side  collar  and  nut  being  used  as  shown.  The  bushing  plate 
set  over  the  work  is  located  to*  bring  the  holes  in  right  relation  with 
the  slots,  by  a  tongue  entering  the  latter.  In  the  next  operation  the 
covers  are  mounted  on  a  special  faceplate,  as  shown  in  Fig.  41.  This 
faceplate  is  surfaced  true  in  place  and  is  provided  with  an  expansion 
mandrel  centered  integrally  with  it.  The  gear  case  is  slipped  on  over 
this  mandrel  and  tightened  in  place  by  turning  on  a  wedge  screw. 
While  thus  held  the  countersink  in  the  outer  end  of  the  hub,  the  seat 
for  the  ball  bearing,  and  the  threaded  diameter  are  turned.  The 
thread  is  also  cut.  This  is  done  by  the  Rivett-Dock  threading  tool, 
shown  in  operation.  These  operations  of  countersinking,  turning  and 
threading,  altogether,  average  about  eight  minutes  time  for  each 
piece.  When  the  turning  was  in  progress,  the  writer  timed  the  lathe 


MAKING  EQUALIZING  GEARS 


41 


and   found   it  was  making   250   revolutions   per   minute,   which   gives 
about  150  surface  feet  per  minute  for  the  cutting  speed. 

A  fixture  and  mill  of  obvious  construction  are  used  for  cutting  the 
keyway  by  which  the  inner  race  of  the  ball-bearing  is  made  fast  to 
the  hub. 

Equalizing-  Pinions,  Studs  and  Gears 

Studs  E,  Fig.  32,  are  made  on  the  Gridley  automatic  turret  lathe  with 
the  regular  tools  and  equipment,  the  job  being,  of  course,  one  of  the 
everyday  variety  for  this  machine.  Oil  grooves  are  milled,  and  then 
the  burrs  are  removed  by  hand.  The  equalizing  pinions  are  drilled, 
reamed  and  turned  on  the  flat  turret  lathe.  The  ends  are  squared 
accurately  to  length  in  the  engine  lathe. 


Fig.  41.    Threading  the  Gear  Case  Covers  with  a  Rivett-Dock  Threading  Tool 

The  equalizing  gears  are  cut  off  to  length  from  the  bar  stock  (all 
gears  and  pinions  are  made  of  chrome-nickel  steel)  and  are  bored, 
reamed,  faced  and  filleted  at  the  large  end  in  the  Jones  &  Lamson 
machine.  The  hole  is  reamed  accurately  to  size  so  as  to  furnish  a 
guide  for  the  broach  in  forming  a  square  hole.  This  is  done  on  the 
La  Pointe  machine  at  a  single  pass  of  the  broach,  which  is  a  long 
one,  having  some  24  inches  or  thereabouts  of  cutting  length.  The 
outside  surfaces  of  the  gear  are  then  rough  turned  on  a  square  expan- 
sion chuck  somewhat  similar  to  that  shown  in  Fig.  41  for  the  gear 
case  cover,  except,  of  course,  that  it  is  mounted  on  a  square  surface 
instead  of  a  round  one.  In  the  next  operation  it  is  finish  turned 
all  over. 

The  spur  gears  and  pinions  are  cut  in  a  triple  head  indexing  device 
which  is  one  of  the  standard  attachments  on  the  Brown  &  Sharpe 
milling  machine.  Three  cutters  operate  on  three  gangs  of  work 
simultaneously.  By  giving  special  shapes  to  the  gears  and  by  being 
very  careful,  both  in  centering  the  cutters  and  setting  them  to  the 


42  No.  60— AUTOMOBILE  CONSTRUCTION 

proper  depth,  first-class  results  have  been  obtained — better  than  are 
needed  in  fact,  since  normally  these  gears  are  stationary  or  nearly 
so,  being  in  operation  only  when  rounding  corners,  in  the  case  of  a 
deflated  tire  on  one  side,  or  the  slipping  of  a  wheel  in  the  mud.  After 
removing  the  burrs  by  file  and  reamer,  the  gears  and  pinions  are 
hardened  by  the  regular  process  recommended  by  the  makers  of  the 
steel  (the  Carpenter  Steel  Co.),  with  such  modifications  as  the  black- 
smith of  the  shop  lias  found  advisable. 

The  equalizing  gear  bushings  D  and  D',  Fig.  32,  are  cut  from  a  bronze 
bar  in  the  flat  turret  lathe,  being  turned  and  bored  complete  to  size. 
A  stack  of  them  are  placed  on  the  Mitts  &  Merrill  keyseater  for  cut- 
ting the  internal  oil  grooves.  The  radial  oil  groove  is  cut  on  the 


Fig.  42.    A  Special  Fixture  for  Cutting  Oil  Grooves  in  the 

Equalizing  Gear  Bushing- 
Interesting  tool  shown  in  Fig.  42.  This  device  is  a  modification  of 
the  principle  used  in  attachments  for  slotting  screws  with  a  saw 
held  in  the  speed  lathe.  The  knurled  handle  shown  controls  three 
motions.  By  screwing  it  in  or  out  the  bushing  is  tightened  or  released 
in  the  jaws  by  which  it  is  held.  Tripping  it  up  or  down  drops  the 
bushing  away  from  or  brings  it  up  toward  the  revolving  cutter,  while 
springing  it  to  one  side  brings  the  bushing  out  from  under  the  cutter 
where  it  can  be  removed  without  interference.  A  wire  finger  locates 
the  work  with  relation  to  the  internal  groove  previously  cut. 

Assembling- 

The  operation  of  assembling  the  parts  to  make  the  complete  mechan- 
ism includes  some  operations  worthy  of  notice.  In  Fig.  43  is  a  case 
assembled  with  its  two  covers,  and  dropped  into  a  cast-iron  reaming 
stand,  where  it  is  held  from  revolving  by  the  projecting  pin  shown, 
which  enters  one  of  the  three  holes  in  its  periphery.  A  line  reamer  is 
used,  giving  assurance  that  the  two  bearings  in  each  cover  will  be 


MAKING  EQUALIZING  GEARS  43 

true  with  each  other.  After  this  line  reaming  the  covers  are  marked, 
numbered  and  burred  so  that  the  same  parts  will  be  reassembled 
together. 

Studs  E  are  next  riveted  to  the  covers,  three  on  one  side  and  three 
on  the  other,  a  hand  hammer  being  used  for  this  purpose.  The  ends 
of  the  rivets  are  cupped  to  facilitate  this  operation.  The  pinions  are 
assembled  on  the  studs,  three  on  each  side.  The  bushings  are  pressed 


Fig.  43.    Line-reaming  the  Pivot  Holes  in  the  Assembled 
Gear  Cases  and  Covers 

into  the  covers  under  the  arbor  press,  and  burred.  The  equalizing 
gears  C  and  C"  are  dropped  into  place  and  the  whole  structure  is  then 
assembled.  A  square  wrench  inserted  through  the  bore  into  the 
squared  hole  in  (7,  permits  the  gears  to  turn  until  they  are  all  en- 
gaged. Three  bolts  and  nuts  G  and  G'  are  now  passed  through,  bind- 
ing the  whole  solidly  together. 

It  is  of  extreme  importance  in  the  quiet  running  of  an  automobile 
that  the  bevel  gears  run  true.  For  this  purpose  the  bevel  gear  seat 
on  the  outside  diameter  of  the  casing  is  not  finish  turned  until  it 
has  been  assembled  as  described.  To  do  this,  the  mechanism  is 


44 


No.  60— AUTOMOBILE  CONSTRUCTION 


mounted  on  the  lathe  on  large  centers,  bearing  on  the  countersinks 
in  A  and  A'.  These  countersinks,  being  formed  in  the  same  operation 
with  the  ball  bearing  seats  and  the  threads,  are  true  with  them.  After 
this  turning  and  facing,  a  jig  fitting  on  this  accurate  seat  is  used  for 
drilling  the  flange  holes  through  which  screws  H  pass  to  fasten  the 
bevel  gear  to  the  casing. 

The  gear  is  pressed  into  place  in  its  seat  by  a  simple  contrivance 
which  illustrates  the  demand  for  conveniences  created  by  the  prem- 


Fig.  44.    A  Convenient  Fixture  for  Assembling  the  Gears 
on  the  Gear  Case 

ium  system.  On  the  bench  in  front  of  the  workman  is  a  cast-iron 
seat  (Fig.  44)  in  which  the  bevel  gear  is  placed  face  downward.  The 
complete  differential  mechanism  is  then  placed  over  the  gear  in  a 
position  to  be  forced  down  into  it.  The  workman  now  reaches  up 
above  his  head  and  brings  down  the  hand-wheel,  clamping  screw  and 
clamp  shown,  which  is  suspended  by  a  counterweight  so  as  to  move 
freely  up  and  down  and  remain  stationary  in  any  position.  Entering 
the  screw  in  the  n-ut  in  the  base  of  the  device  and  turning  the  hand- 
wheel,  forces  the  casing  down  into  the  gear  and  thus  completes  the 


MAKING  EQUALIZING  GEARS 


45 


assembling.  The  tap  bolts  are  now  put  in  and  are  wired  through 
holes  drilled  through  their  heads,  to  prevent  them  from  turning.  This 
completes  the  making  of  the  equalizing  gear. 

A  Good  Tapping-  Record 

While  the  making  of  the  bevel  gear  has  not  been  described,  it  will 
not  do  to  pass  over  one  of  the  operations  met  with.  This  is  the  opera- 
tion of  tapping  the  holes  by  which  the  gear  is  held  to  the  flange. 
These  holes  are  5-16  inch  in  diameter  and  13-16  inch  deep  and  are 


Fig-  45.    A  Tapping  Operation  and  Operator  with  a  Remarkable  Record— 
75,OOO  Blind  5-16-inch  Holes  in  Chrome-nickel  Steel  without  breaking  a  Tap 

blind,  being  tapped  to  a  bottom  and  not  through.  The  tapping  is 
done  in  a  Cincinnati  drill  press  (Fig.  45),  using  an  Errington  friction 
chuck.  Tapping  in  chrome-nickel  steel  by  power  is,  it  will  be  agreed, 
no  "fool  of  a  job."  One  of  the  difficulties  met  with  is  the  tendency 
of  the  metal  to  seize  the  tap  and  break  it  when  backing  out. 

The  operator  shown  broke  many  taps  in  becoming  familiar  with  his 
job,  but  since  he  has  gotten  into  the  swing  of  it,  he  has  tapped  75,000 
of  these  blind  holes  in  chrome-nickel  steel  without  breaking  a  tap. 


46 


No.  60— AUTOMOBILE  CONSTRUCTION 


The  credit  of  this  record  must  be  divided  between  the  man,  the  ma- 
chine, the  chuck  and  the  tap,  but  there  is  enough  to  make  a  respectable 
showing  for  all  four.  The  operator's  increase  of  efficiency  was  obtained 
with  practically  no  change  in  the  tools  or  methods,  being  due  simply 
to  the  training  of  his  judgment  in  the  feeling  of  the  tap,  and  in  the 
use  of  excellent  tools.  It  might  be  said  that  a  firm  of  the  highest 


Fig.  46.    A  Completed  Equalizing:  Gear  Set  up  for 
Testing  to  Destruction 


Fig.  47.     Condition  of  Shafts  Broken  in  Tests  shown  In 
Fig.  46 ;   the  Gears  were  Uninjured 

reputation  for  accuracy  and  for  skill  in  manufacturing  had  asked 
ten  cents  a  hole  for  the  job.  This  operator  runs  two  taps  in  each 
of  the  twelve  holes  in  a  gear,  twenty-four  holes  in  all,  in  from  15  to 
IS  minutes. 

Tests  on  the  Finished  Casing-s 

Of  course,  the  object  that  was  aimed  at  in  designing  these  equaliz- 
ing gears  for  sale  to  manufacturers  of  automobiles,  was  to  give  them 
such  strength  that  some  other  part  of  the  machine  would  break  first. 
In  order  to  find  out  whether  or  no  this  result  had  been  obtained  a 


MAKING  EQUALIZING  GEARS  47 

number  of  tests  were  made  in  the  laboratory  of  the  engineering  school 
of  Brown  University.  In  Fig.  46  the  casing  is  shown  as  mounted  in 
brackets  for  a  torsion  test,  the  power  being  applied  through  1-inch, 
3%  per  cent  nickel-steel  shafts,  specially  treated.  These  failed  at 
20,300  inch-pounds,  twisting  through  800  degrees  before  rupture.  Sam- 
ples of  broken  shafts  are  shown  in  Pig.  47,  and  give  some  idea,  in 
combination  with  the  figures  just  given,  of  the  excellence  of  the  ma- 
terial used  in  these  shafts.  No  damage  of  any  kind  was  found  inside 
the  gear  casing,  the  mechanism  being  unbroken  and  running  as  easily 
and  smoothly  as  before. 


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UNIVERSITY  OF  CALIFORNIA  LIBRARY 


CONTENTS  OF  DATA  SHEET  BOOKS 


No.  1.  Screw  Threads.-  r  i  i  t . d  States, 
WhltWOPth,  Sharp  \"-  and  llritish  Associa- 
tion Standard  rriir«-ads;  llriuus  Pipe 
Thread:  oil  Well  Casing  (Safes'  Kin-  Hose 
Com  Thread:  Worm 

Threads;  Metric  Threads:  I'M .tch  ine.  Wood, 
and  La.u  rim-ads;  Carriage  Bolt 

Threads,  etc. 

No.  2.  Screws,  Bolts  and  Nuts. —  ril- 
lister-head.  Square-head.  Headless.  Col- 
and  Hexagon-head  Screws;  Stand- 
aru  and  Special  Nuts;  T-:  <;<s,  T-bolts  and 
Washers;  Tliumb  Screws  aid  Nuts;  A.  L. 
A.  M.  Standard  Se]v\vs  and  Nuts;  Maehine 
Screw  Heads;  AYood  Screws;  Tap  Drills; 
Lock  Nt.ts;  Kye-bolts,  etc, 

No.  3.     Taps  and  Dies. — Hand,  Machine, 

Tapper    and    Maehine    Screw    Taps;    Taper 

dcrs    Hobs;    Screw    Machine 

'laps;     Strai^lit    and    Taper    ];oil?r    Taps; 

-iMilt.    Wa.  iiout.   and    1'ateh-bolt   Taps; 

i   Hobs;   S'llid  Square,    Round 

Adjustable    and    Sp.'in;-    S'     AV    Threading 

^9.  4,  Rc-uners  Sockets,  Drills  and 
Viir.ng  Butters. — .  and  Reamers:  Shell 
1;  auu-r  'ind  Arbo";  ;  Pipe  Reamers;  Taper 
1  us  Ream  \vn  &  Sharpe, 

M'      -e  a  Soc'-fts  and  Ream- 

'•r«  Drills;  Wire  Gugos;  Milling  Cutters; 
Setung  Ang-i-s  for  Milling  Teeth  in  End 
Mills  and  Vngular  Cutters,  etc. 

No.  5.     t»pur    Gearing*. — Diametral    and 

Circular  Pitch;   Dimensions  of  Spur  Gears; 

Tables    of    Pitcn    Diameters;    Odontograph 

Tables:   Rollin  r  Mill  Gearing;  Strength  of 

Spur    Geais;    liorsepo\\.  mitted   by 

-iron  and  Rawhide  Pinions;  Design  of 

-t-iron    Gears; 

rlic  <  it-ai  Ing. 

No.  6.     Bevel,    Spiral   and   Worm   Gear- 
ing1.— Rules      and      1  .-rmulas      for      Bevl 
irength    of    I'.evel    Cieurs;     Design 
s;    Jlules    and    Formulas    for 
Spiral  i-  ibles  Facilitating  Calcu- 

:-am    for    fitters    for    Spiral 
Ruins    and    Formulas    for    Worm 
Ge; 

No.  7.  E  'ting1,  Keys  and  Key  ways. — 
H">  scpow  of  Shafting;  Diagrams  and 
T;.  les  f.,r  the  .strength  of  Shafting; 

'vpr«  5ng,    Driving,    .''hrinking  and   Running 
:    Woodruff   Keys;    United   States   Navy 
•  lard    Keys:    Gib   Keys;    Milling   Key- 
\\avs;    Duplex    Keys. 

TTo.  8.     Bearing's,     Coupling's,     Clutches, 
Crane   Chain   and   Hooks. —  Pillow    Blocks; 
Babbitted    I'.;  rings:    Ball  and   Roller  Bear- 
Clamp    Couplings;    Plate   Couplings; 
•oupling*;    Tooth    Clutches;    Crab 
nqrs;       Cone      Clutches;       Universal 
''rane     Chain;     Chain     Friction; 
Crane  ilool.s;   Drum  Scores. 

No.  9.  Spring's,  Slides  and  Machine 
Detai;0.—  Formulas  and  Tabl.  s  for  Spring 
Calculations;  M.  •  hine  Slid<>s;  Machine 
jIan«:-..-s  ;,nd  I.  vets;  Collars;  Hand 
Wheels;  Pins  and  Cotters;  Turn-buckles, 

No.  10.     Motor  Drive,  Speeds  and  Feeds, 

Change  J-ear^g,  and  Boring1  Bars.      Tower 

i-erjuirod      for      Machine      Tools;      Cutting 

Is   and    Feeds    for   Carbon    and    Iligh- 

:     Sie,-i:     Screw'    Machine    Speeds    and 

Heat      Treatment     of     High-speed 


1  Tools;  Taper  Turning;  Change  G 
ing  for  the  Lathe;   Boring  Bars  and  T 

No.  11.  Milling-  Machine  Indexing1, 
Clamping;  Devices  and  Planer  Jacks. — 

Tables      for     Milling     Machine.      lnde\ 
Cha  for  Milling   Spirals;   Ai 

for   setting    Indexing    Head    when    Milling 
Clutches;    Jig    Clamping    J 
and  Clamps;  Plant  r  Jacks. 

No.  12.     Pipe   and  Pipe   Fittings.-  pip,. 
Threads    and    Gages;    Cast-iron    Fiti 
Bronze      Fittings;      Pipe      Flan^ 
Bends;  Pipe  Clamps  anil  Han.u< 
sions  of  Pipe  for  Various  Service 

No.  13.  Boilers  and  Chimney b  —Fine 
Spacing  and  Bracing  for  Boilers;  Sin-ngth 
of  Boiler  Joints;  Riveting;  Boiler  Setting; 
Chimneys. 

No.  14.    locomotive  and  Railway  I>ata. 
— Locomotive    Boilers;   Beaii-g   Pi    -;sui  -. 
for      Locomotive      Journals;       L<><-       »{i\< 
Classifications;      Rail      Sections;          ro^s. 
Switches  and  Cross-overs;  Tires; 
Force;    Inertia  of   Traias;    Brake 
Brake  Rods,  etc. 

No.   15.    Steam  and  Gas  Engine     —  Sat- 
urated   St^am;    Stem    Pipe    Six. 
Kngino     Design;      Volume     of     C 
Stuffiing    Boxes;    Setting    Corliss     Kn 
Valve    Gears;    Condenser    and    Air    J'unn. 
Data;    Horsepower    of    Gasoline 
Automobile    .Engine    Crankshafts,    otc. 

No.  16.     Mathematical  Tables.-    Squares 
of    Mixed    Number:;;    Functions    o      J 
tions;    Circumference    and    Diame    :rs 
Circles;    'l^ables    for    Spacing    off    Circles: 
Solution  of  Triangles;  Formulas  f<  :  Solv- 
ing   Regular   Polygons;    Geometric   !    Pr-  - 
gression.  etc. 

No.  17.  Mechanics  and  Strength  ->t  Ma- 
terials.— Work;  Energy;  Centrifugal 
Force;  Center  of  Gravity;  Motion;  Fric- 
tion; Pendulum;  Falling  Bodies;  S  *-engtli 
of  Materials;  Strength  of  Flat  la 
Ratio  of  outside  and  Irside  R  ill  "f 
Thick  Cylinders,  etc. 

No.  18.  Beam  Formulas  and  Str^cta-.:! 
Design. — Beam  Formulas;  S-  io.i- 

uli    of    Structural    Shapes;    Beam       .iarts 
Net    Areas    of    Structural    Angles      Rivet 
Spacing;     Splices     for     Channels     .<nd     I- 
beams;   Stresses   in   Roof  Trusses, 

No.  19:     Belt,  Hope  and  Chain  Drives. 
Dimensions    of    Pulleys;    Weights   of   Pul- 
leys;   Horsepower  of  Belting;  Belt  Veloc- 
ity;    Angular    Belt     Drives;     Horsepower 
transmitted    by    l:opes;    Sheaves    for    i: 
Drive:    Bending   Stresses    in    Wii 
Sprockets  for   Link  Chains;   Formulas  and 
Tables     for     Various     Classes    of     Driving 
Chain. 

No.  20.     Wiring1  Diagrams,  Heating1  and 
Ventilation,    and    Miscellaneous    Tables. — 
Typical   Motor   Wiring    1  .'iagramv 
ance  of  Round  Copper  'Wire;   itui 

:  Cables;  Current  Densities  IVr  \ 
ous  Contacts  and  Materials;  Centrlf 
Fan  and  Blower  Capacities;  H,,t  \v 
Main  Capacities;  Miscellaneous  Tal 
Decimal  Equivalents,  Metric  Conver 
Tables.  \\'i-i^lits  and  Specific  Gravity  of 
IB,  \Vei-his  of  l-'illets.  Drafting  i 

Conventions,    • 


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